Advanced treatment process and system for thiourea-containing wastewater

Abstract

According to the advanced treatment process for the thiourea-containing wastewater, multi-stage pretreatment is performed through iron-carbon micro-electrolysis, three-dimensional electrochemical oxidation and ozone oxidation, so that long-chain organic matters are degraded, organic nitrogen is directly converted into nitrogen, and the biodegradability of the wastewater is improved; then adjusting the pH value, and sequentially carrying out biochemical treatment through an IC tower and a biological contact oxidation pond; and biochemical effluent is finally subjected to ozone contact oxidation to ensure that the standard is reached. According to the invention, iron-carbon micro-electrolysis, three-dimensional electrochemical oxidation and ozone oxidation are sequentially adopted to carry out multi-stage pretreatment on the wastewater, so that long-chain organic matters are efficiently degraded, organic nitrogen is directly converted into nitrogen, and the biodegradability of the wastewater is remarkably improved; then adjusting the pH value of the wastewater to be neutral, and sequentially introducing the wastewater into an IC tower and a biological contact oxidation pond to realize degradation of short-chain organic matters and efficient biological denitrification; and finally, residual refractory pollutants are further removed through ozone contact oxidation, so that stable and thorough purification of high-toxicity, high-ammonia-nitrogen and high-COD thiourea-containing wastewater is realized.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a deep treatment process and system for thiourea-containing wastewater. Background Technology

[0002] Thiourea is highly toxic and can enter the human body through a wide range of pathways. Thiourea-producing wastewater (such as fumaric acid wastewater) often has a low pH value, and the organic nitrogen in thiourea results in high ammonia nitrogen levels, leading to a type of recalcitrant wastewater characterized by low pH, high ammonia nitrogen, and high COD. Direct discharge of this type of wastewater will cause serious harm to the aquatic environment and ecosystem.

[0003] Currently, chemical oxidation processes such as micro-electrolysis, Fenton oxidation, and hydrogen peroxide oxidation are commonly used to treat thiourea wastewater. However, these single chemical oxidation methods often fail to completely decompose organic nitrogen and long-chain organic matter in the wastewater, resulting in effluent quality that cannot consistently meet discharge standards. Furthermore, traditional chemical oxidation methods suffer from problems such as large reagent dosages, high operating costs, and the potential for secondary pollution and hazardous waste generation, limiting their application in practical engineering projects.

[0004] Therefore, how to achieve efficient and thorough removal of various pollutants from thiourea wastewater, especially given its complex pollution characteristics of low pH, high toxicity, high ammonia nitrogen, and high COD, has become a pressing technical challenge in this field. Summary of the Invention

[0005] This invention proposes an advanced treatment process and system for thiourea-containing wastewater, which solves the problems of incomplete pollutant removal and high operating costs in the treatment of thiourea wastewater by the single chemical oxidation method in the prior art.

[0006] The technical solution of this invention is implemented as follows: The first aspect of this invention provides a deep treatment process for thiourea-containing wastewater, comprising the following steps: Thiourea-containing wastewater is fed into an iron-carbon micro-electrolysis tower, where iron-carbon packing material is used to perform preliminary oxidation and chain breaking of long-chain organic matter in the wastewater under the reaction of a galvanic cell. Wastewater treated by iron-carbon micro-electrolysis is fed into a three-dimensional electrochemical reactor, where organic nitrogen in the wastewater is directly oxidized into nitrogen gas under the action of hydroxyl radicals, and organic matter is further degraded. Wastewater treated by a three-dimensional electrochemical reactor is fed into an ozone oxidation tank, where ozone is used to deeply oxidize residual organic matter and incompletely oxidized organic nitrogen in the wastewater. The deeply oxidized wastewater is passed into a pH buffer tank, and the pH value of the wastewater is adjusted using alkaline agents. The pH-adjusted wastewater is fed into an anaerobic internal circulation reaction tower, where anaerobic microorganisms are used for denitrification and degradation of short-chain organic matter. The anaerobic wastewater is fed into a biological contact oxidation tank, where nitrification is carried out using an aerobic biofilm to convert ammonia nitrogen into nitrate and further remove biodegradable organic matter. The effluent after biochemical treatment is fed into an ozone contact oxidation tower, where ozone is used to finally oxidize the remaining recalcitrant organic matter, ensuring that the effluent meets discharge standards.

[0007] Specifically, the iron-carbon micro-electrolysis tower has an iron-carbon packing ratio of 70% to 90%, a reaction time of 1 to 1.5 hours, and aeration and mixing are carried out during the reaction process at an aeration rate of 1 to 1.5 L / min, so that the COD concentration of the wastewater decreases from 10 to 14 g / L to 8.0 to 8.5 g / L, and the ammonia nitrogen concentration decreases from 1900 to 2100 mg / L to 1850 to 1950 mg / L.

[0008] Specifically, the anode of the three-dimensional electrochemical reactor is a DSA anode, the cathode is a titanium plate, the reactor is filled with activated carbon three-dimensional particle electrodes, the power supply voltage is 20-30V, the reaction time is 0.3-0.7 hours, and aeration and mixing are carried out during the reaction process at an aeration rate of 4-6L / min, so that the COD concentration of the wastewater is reduced to 4.5-5.0g / L and the ammonia nitrogen concentration is reduced to 400-450mg / L.

[0009] Specifically, the ozone concentration in the ozone oxidation tank is 40-60 mg / L, and the reaction time is 0.3-0.7 hours, so that the COD concentration of the wastewater is reduced to 2.0-2.4 g / L and the ammonia nitrogen concentration is reduced to 120-140 mg / L.

[0010] Specifically, the alkaline agent is a sodium carbonate solution, and the dosage is 0.8–1.2 g / L of wastewater, which raises the pH value of the wastewater from 1–1.5 to 6–8.

[0011] Specifically, the internal circulation ratio of the anaerobic internal circulation reactor is 150% to 250%, and the reaction time is 20 to 28 hours, so that the COD concentration of the wastewater is reduced to 1.4 to 1.6 g / L and the ammonia nitrogen concentration is reduced to 45 to 55 mg / L.

[0012] Specifically, the biological contact oxidation tank is equipped with biological packing material, the reaction time is 20 to 28 hours, and aeration is carried out during the reaction process at an aeration rate of 3.5 to 5.5 L / min, so that the COD concentration of the wastewater is reduced to 350 to 400 mg / L and the ammonia nitrogen concentration is reduced to 20 to 25 mg / L.

[0013] Specifically, the ozone contact oxidation tower is filled with aeration packing material with a filling rate of 70% to 90%, the ozone dosage is 40 to 60 mg / L, the reaction time is 0.5 to 1.5 hours, the aeration rate is 3.5 to 5.5 L / min, and the final effluent COD concentration is reduced to 110 to 120 mg / L and the ammonia nitrogen concentration is reduced to 8 to 10 mg / L.

[0014] A second aspect of the present invention provides an advanced treatment system for thiourea-containing wastewater, comprising: Iron-carbon micro-electrolysis tower is used for the preliminary oxidation and chain breaking of long-chain organic matter in wastewater; A three-dimensional electrochemical reactor is used to directly oxidize organic nitrogen in wastewater into nitrogen gas and further degrade organic matter; Ozone oxidation ponds are used for the deep oxidation of residual organic matter and incompletely oxidized organic nitrogen in wastewater. A pH buffer tank is connected to an alkali dosing device, which is used to add alkaline agents to the pH buffer tank to adjust the pH value of the wastewater. Anaerobic internal circulation reaction tower is used for denitrification and degradation of short-chain organic matter; Biological contact oxidation tanks are used to carry out nitrification to convert ammonia nitrogen into nitrate and degrade residual organic matter; Ozone contact oxidation towers are used for the final oxidation of residual recalcitrant organic matter in wastewater.

[0015] Preferably, a nitrification liquid return pipeline is connected between the anaerobic internal circulation reactor and the biological contact oxidation tank, and the return pipeline is used to transport the nitrification liquid generated by the biological contact oxidation tank to the anaerobic internal circulation reactor.

[0016] Compared with existing technologies, the advantages of this invention are as follows: This invention pre-treats wastewater through a multi-stage process of iron-carbon micro-electrolysis, three-dimensional electrochemical oxidation, and ozone oxidation, which efficiently degrades long-chain organic matter, directly converts organic nitrogen into nitrogen gas, and significantly improves the biodegradability of wastewater. Subsequently, the pH of the wastewater is adjusted to neutral and then sequentially fed into an anaerobic internal circulation reactor and a biological contact oxidation tank to achieve the degradation of short-chain organic matter and efficient biological denitrification. Finally, ozone contact oxidation further removes residual recalcitrant pollutants, thereby achieving stable and thorough purification of highly toxic, high ammonia nitrogen, and high COD thiourea-containing wastewater. The effluent quality can stably meet the discharge standards. Furthermore, the nitrified liquid generated in the biological contact oxidation tank is supplied to the anaerobic internal circulation reactor for reaction through a return pipeline, reducing the system operating cost. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic flow diagram of an advanced treatment process for thiourea-containing wastewater according to the present invention. Detailed Implementation

[0019] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] Reference Figure 1 The first aspect of this invention provides a deep treatment process for thiourea-containing wastewater, comprising the following steps: Thiourea-containing wastewater is fed into an iron-carbon micro-electrolysis tower, where iron-carbon packing material is used to perform preliminary oxidation and chain breaking of long-chain organic matter in the wastewater under the reaction of a galvanic cell. Wastewater treated by iron-carbon micro-electrolysis is fed into a three-dimensional electrochemical reactor, where organic nitrogen in the wastewater is directly oxidized into nitrogen gas under the action of hydroxyl radicals, and organic matter is further degraded. Wastewater treated by a three-dimensional electrochemical reactor is fed into an ozone oxidation tank, where ozone is used to deeply oxidize residual organic matter and incompletely oxidized organic nitrogen in the wastewater. The deeply oxidized wastewater is passed into a pH buffer tank, and the pH value of the wastewater is adjusted using alkaline agents. The pH-adjusted wastewater is fed into an anaerobic internal circulation reaction tower, where anaerobic microorganisms are used for denitrification and degradation of short-chain organic matter. The anaerobic wastewater is fed into a biological contact oxidation tank, where nitrification is carried out using an aerobic biofilm to convert ammonia nitrogen into nitrate and further remove biodegradable organic matter. The effluent after biochemical treatment is fed into an ozone contact oxidation tower, where ozone is used to finally oxidize the remaining recalcitrant organic matter, ensuring that the effluent meets discharge standards.

[0021] The core mechanism of this invention lies in its three-stage synergistic treatment system, designed to address the complex pollution characteristics of thiourea wastewater, which are characterized by low pH, high toxicity, high ammonia nitrogen, and high COD. Pretreatment stage: First, utilizing the extremely low acidity of the wastewater, a "galvanic cell reaction" is carried out in an iron-carbon micro-electrolysis tower. That is, under low pH conditions, carbon and iron are used as electrodes to carry out a discharge reaction, and H2O is generated through the electrode reaction. + The coagulation effect of strong reducing substances such as Fe²⁺ and iron ions achieves preliminary chain breaking and partial degradation of long-chain and complex organic compounds, not only reducing COD but also converting large molecular toxins into small molecular intermediates, creating favorable conditions for subsequent oxidation. Subsequently, under the action of an electric field, the three-dimensional electrochemical reactor achieves the synergistic effect of direct anodic oxidation, cathodic reduction, and the generation of strong oxidizing hydroxyl radicals (·OH) on the surface of the filled activated carbon particle electrodes, thereby reducing organic nitrogen (such as -N in thiourea molecules). The efficient and targeted oxidation of ozone directly converts it into N2, thus significantly reducing total nitrogen and further decreasing toxicity during the pretreatment stage. Finally, the ozone oxidation tank utilizes the strong oxidizing properties of ozone molecules (O3) and the ·OH produced by their decomposition to deeply oxidize the recalcitrant small-molecule organic matter and organic nitrogen remaining from the first two oxidation stages, thoroughly weakening the toxicity of the wastewater and oxidizing and degrading organic matter, thereby achieving the degradation of toxic substances and removal of ammonia nitrogen from acidic, highly toxic, and high-ammonia-nitrogen wastewater.

[0022] Biological Treatment Stage: Pretreated wastewater enters the biological treatment system after pH adjustment. The anaerobic internal circulation reactor maintains a high internal circulation ratio, creating a strong upward flow velocity and sludge circulation, thus providing excellent hydraulic mixing and mass transfer conditions. Denitrifying bacteria enriched within the reactor utilize short-chain organic matter in the influent as carbon and electron donors to denitrify nitrate nitrogen provided by the nitrification liquid recirculation, reducing it to N2. Simultaneously, anaerobic ammonia-oxidizing bacteria, which may be present, can perform short-cut denitrification. This process removes some COD while efficiently removing nitrogen. The aerobic biofilm attached and growing in the biological contact oxidation tank provides a favorable habitat for nitrifying bacteria. Under sufficient aeration, nitrifying bacteria gradually oxidize ammonia nitrogen in the wastewater to nitrite and nitrate, completing the nitrification process. This achieves the removal of most organic matter and ammonia nitrogen, ultimately maximizing the toxicity of thiourea wastewater and degrading organic matter.

[0023] Advanced treatment stage: Biochemical effluent may still contain residual recalcitrant COD and nitrogen-containing organic matter. The ozone contact oxidation tower, with the addition of packing material, increases the contact area between ozone and wastewater, improving the treatment effect. It can finally degrade the residual recalcitrant COD and nitrogen-containing organic matter in the biochemical effluent, thereby ensuring that the wastewater fully meets the standards.

[0024] Specifically, the iron-carbon micro-electrolysis tower has an iron-carbon packing ratio of 70% to 90%, a reaction time of 1 to 1.5 hours, and aeration and mixing are carried out during the reaction process at an aeration rate of 1 to 1.5 L / min, so that the COD concentration of the wastewater decreases from 10 to 14 g / L to 8.0 to 8.5 g / L, and the ammonia nitrogen concentration decreases from 1900 to 2100 mg / L to 1850 to 1950 mg / L.

[0025] Specifically, the anode of the three-dimensional electrochemical reactor is a DSA anode, the cathode is a titanium plate, the reactor is filled with activated carbon three-dimensional particle electrodes, the power supply voltage is 20-30V, the reaction time is 0.3-0.7 hours, and aeration and mixing are carried out during the reaction process at an aeration rate of 4-6L / min, so that the COD concentration of the wastewater is reduced to 4.5-5.0g / L and the ammonia nitrogen concentration is reduced to 400-450mg / L.

[0026] Specifically, the ozone concentration in the ozone oxidation tank is 40-60 mg / L, and the reaction time is 0.3-0.7 hours, so that the COD concentration of the wastewater is reduced to 2.0-2.4 g / L and the ammonia nitrogen concentration is reduced to 120-140 mg / L.

[0027] Specifically, the alkaline agent is a sodium carbonate solution, and the dosage is 0.8–1.2 g / L of wastewater, which raises the pH value of the wastewater from 1–1.5 to 6–8.

[0028] Specifically, the internal circulation ratio of the anaerobic internal circulation reactor is 150% to 250%, and the reaction time is 20 to 28 hours, so that the COD concentration of the wastewater is reduced to 1.4 to 1.6 g / L and the ammonia nitrogen concentration is reduced to 45 to 55 mg / L.

[0029] Specifically, the biological contact oxidation tank is equipped with biological packing material, the reaction time is 20 to 28 hours, and aeration is carried out during the reaction process at an aeration rate of 3.5 to 5.5 L / min, so that the COD concentration of the wastewater is reduced to 350 to 400 mg / L and the ammonia nitrogen concentration is reduced to 20 to 25 mg / L.

[0030] Specifically, the ozone contact oxidation tower is filled with aeration packing material with a filling rate of 70% to 90%, the ozone dosage is 40 to 60 mg / L, the reaction time is 0.5 to 1.5 hours, the aeration rate is 3.5 to 5.5 L / min, and the final effluent COD concentration is reduced to 110 to 120 mg / L and the ammonia nitrogen concentration is reduced to 8 to 10 mg / L.

[0031] A second aspect of the present invention provides an advanced treatment system for thiourea-containing wastewater, comprising: Iron-carbon micro-electrolysis tower is used for the preliminary oxidation and chain breaking of long-chain organic matter in wastewater; A three-dimensional electrochemical reactor is used to directly oxidize organic nitrogen in wastewater into nitrogen gas and further degrade organic matter; Ozone oxidation ponds are used for the deep oxidation of residual organic matter and incompletely oxidized organic nitrogen in wastewater. A pH buffer tank is connected to an alkali dosing device, which is used to add alkaline agents to the pH buffer tank to adjust the pH value of the wastewater. Anaerobic internal circulation reaction tower is used for denitrification and degradation of short-chain organic matter; Biological contact oxidation tanks are used to carry out nitrification to convert ammonia nitrogen into nitrate and degrade residual organic matter; Ozone contact oxidation towers are used for the final oxidation of residual recalcitrant organic matter in wastewater.

[0032] Preferably, a nitrification liquor return pipeline connects the anaerobic internal circulation reactor and the biological contact oxidation tank. This return pipeline transports the nitrified liquor produced in the biological contact oxidation tank to the anaerobic internal circulation reactor. A return pump installed within the tank quantitatively returns the nitrate-rich nitrified liquor to the upstream IC tower, providing the necessary electron acceptor for denitrification, thus forming a complete "nitrification-denitrification" biological denitrification closed loop. This coupled design fully utilizes the carbon source of the original wastewater, resulting in high denitrification efficiency and low sludge production.

[0033] To repeatedly verify the beneficial effects of the present invention, several detailed embodiments and comparative examples are provided below. The raw water treated in all cases was the same batch of thiourea wastewater with the following characteristics: pH=1.8, COD concentration of 12500 mg / L, and ammonia nitrogen concentration of 2050 mg / L.

[0034] Example 1

[0035] Iron-carbon micro-electrolysis tower: iron-carbon packing ratio 80%, reaction time 3 hours, aeration rate 3 L / min.

[0036] Three-dimensional electrochemical reactor: power supply voltage 25 V, reaction time 0.5 h, aeration rate 5 L / min.

[0037] Ozone oxidation tank: ozone concentration 50 mg / L, reaction time 0.5 hours.

[0038] pH adjustment: Add 1.0 g / L sodium carbonate to adjust the pH to 7.0.

[0039] Anaerobic internal circulation reaction tower (IC tower): internal circulation ratio 200%, reaction time 24 hours.

[0040] Biological contact oxidation tank: reaction time 24 hours, aeration rate 4.5 L / min.

[0041] Ozone contact oxidation tower: ozone concentration 50 mg / L, reaction time 1 hour, packing filling rate 80%.

[0042] Final effluent quality: COD 117 mg / L, ammonia nitrogen 9.0 mg / L.

[0043] Overall operating cost (electricity consumption, chemicals, etc.): approximately RMB 15.8 per ton of wastewater.

[0044] Example 2

[0045] Iron-carbon micro-electrolysis tower: iron-carbon packing ratio 70%, reaction time 2 hours, aeration rate 2 L / min.

[0046] Three-dimensional electrochemical reactor: power supply voltage 20 V, reaction time 0.3 h, aeration rate 4 L / min.

[0047] Ozone oxidation tank: ozone concentration 40 mg / L, reaction time 0.3 hours.

[0048] pH adjustment: Add 0.8 g / L sodium carbonate to adjust the pH to 6.0.

[0049] Anaerobic internal circulation reaction tower (IC tower): internal circulation ratio 150%, reaction time 20 hours.

[0050] Biological contact oxidation tank: reaction time 20 hours, aeration rate 3.5 L / min.

[0051] Ozone contact oxidation tower: ozone concentration 40 mg / L, reaction time 0.5 hours, packing filling rate 70%.

[0052] Final effluent quality: COD 135 mg / L, ammonia nitrogen 11.5 mg / L.

[0053] Overall operating cost (electricity consumption, chemicals, etc.): approximately RMB 14.2 per ton of wastewater.

[0054] Example 3

[0055] Iron-carbon micro-electrolysis tower: iron-carbon packing ratio 90%, reaction time 4 hours, aeration rate 4 L / min.

[0056] Three-dimensional electrochemical reactor: power supply voltage 30 V, reaction time 0.7 h, aeration rate 6 L / min.

[0057] Ozone oxidation tank: ozone concentration 60 mg / L, reaction time 0.7 hours.

[0058] pH adjustment: Add 1.2 g / L sodium carbonate to adjust the pH to 8.0.

[0059] Anaerobic internal circulation reaction tower (IC tower): internal circulation ratio 250%, reaction time 28 hours.

[0060] Biological contact oxidation tank: reaction time 28 hours, aeration rate 5.5 L / min.

[0061] Ozone contact oxidation tower: ozone concentration 60 mg / L, reaction time 1.5 hours, packing filling rate 90%.

[0062] Final effluent quality: COD 105 mg / L, ammonia nitrogen 7.8 mg / L.

[0063] Overall operating cost (electricity consumption, chemicals, etc.): approximately RMB 19.5 per ton of wastewater.

[0064] The following comparative examples are all based on Example 1, with only one process parameter changed, while the other parameters are exactly the same as in Example 1. The results are shown in the table below: Table 1 Comparative Example: Process Parameters and Effluent Parameters

[0065] From the comprehensive embodiments and comparative examples, it can be seen that: When key process parameters fall below the set lower limit, as in Comparative Examples 1-4, the corresponding treatment unit cannot function, resulting in severe exceedances of COD, ammonia nitrogen, or total nitrogen in the effluent, leading to process failure. Although its overall cost (approximately RMB 12.5-14.0 per ton) may be slightly lower than that of Example 1, cost savings achieved at the cost of treatment failure are not practically meaningful.

[0066] When key process parameters exceed the set upper limit, such as in Comparative Examples 5-6, although stable or even slightly better effluent quality can be obtained, the overall cost (21.5-24.2 yuan / ton) increases significantly by 35%-53% compared to Example 1 (15.8 yuan / ton), while the effect of improving water quality is limited.

[0067] Comparing Examples 1-3: Example 1 achieved the best balance between treatment effect (effluent COD 117 mg / L, ammonia nitrogen 9.0 mg / L) and overall cost (15.8 yuan / ton). Although Example 2 had a low cost (14.2 yuan / ton), its effluent indicators had a small margin and weak shock resistance. Example 3 had the best effluent, but its cost was too high (19.5 yuan / ton), resulting in low cost-effectiveness.

[0068] Comparative Example 7

[0069] Raw water quality: Same as in Example 1.

[0070] Process sequence adjustment: The "pH adjustment" step is moved forward to before "iron-carbon micro-electrolysis". That is, sodium carbonate is added to the raw water first to adjust the pH to 7.0, and then all subsequent treatment steps are carried out (iron-carbon micro-electrolysis → three-dimensional electrochemistry → ozone oxidation → IC tower → biological contact oxidation → ozone contact oxidation).

[0071] The process parameters for each unit are exactly the same as those in Example 1.

[0072] Final effluent quality: COD 650 mg / L, ammonia nitrogen 55 mg / L.

[0073] The core mechanism of the iron-carbon micro-electrolysis reaction in this invention relies on the low pH (acidic) environment of the wastewater itself. Under low pH conditions, iron and carbon form a galvanic cell with a significant potential difference, continuously generating highly reactive H₂. + Fe 2+ The same substances, and Fe generated at the same time 2+ / Fe 3+ It exhibits good coagulation and adsorption properties. However, because the pH of Comparative Example 7 was adjusted to neutral (7.0) beforehand, the driving force (potential difference) of the galvanic cell reaction was drastically weakened, resulting in severe electrode polarization and a sharp decrease in the production of active substances. This essentially rendered the synergistic effect of "electrochemical oxidation-reduction-coagulation" in micro-electrolysis ineffective. Consequently, the chain breaking of long-chain organic matter was insufficient, the pretreatment effect was significantly reduced, and the treatment load of all subsequent oxidation and biochemical units far exceeded the design capacity. Toxic substances and ammonia nitrogen were not effectively removed, ultimately leading to severe deterioration of the effluent quality.

[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A deep treatment process for thiourea-containing wastewater, characterized in that, Includes the following steps: Thiourea-containing wastewater is fed into an iron-carbon micro-electrolysis tower, where iron-carbon packing material is used to perform preliminary oxidation and chain breaking of long-chain organic matter in the wastewater under the reaction of a galvanic cell. Wastewater treated by iron-carbon micro-electrolysis is fed into a three-dimensional electrochemical reactor, where organic nitrogen in the wastewater is directly oxidized into nitrogen gas under the action of hydroxyl radicals, and organic matter is further degraded. Wastewater treated by a three-dimensional electrochemical reactor is fed into an ozone oxidation pond, where ozone is used to deeply oxidize residual organic matter and incompletely oxidized organic nitrogen in the wastewater. The deeply oxidized wastewater is passed into a pH buffer tank, and the pH value of the wastewater is adjusted using alkaline agents. The pH-adjusted wastewater is fed into an anaerobic internal circulation reaction tower, where anaerobic microorganisms are used for denitrification and degradation of short-chain organic matter. The anaerobic wastewater is fed into a biological contact oxidation tank, where nitrification is carried out using an aerobic biofilm to convert ammonia nitrogen into nitrate and further remove biodegradable organic matter. The effluent after biochemical treatment is fed into an ozone contact oxidation tower, where ozone is used to finally oxidize the remaining recalcitrant organic matter, ensuring that the effluent meets discharge standards.

2. The advanced treatment process for thiourea-containing wastewater as described in claim 1, characterized in that, The iron-carbon micro-electrolysis tower has an iron-carbon packing ratio of 70% to 90%, a reaction time of 1 to 1.5 hours, and aeration and mixing during the reaction process at an aeration rate of 1 to 1.5 L / min. This reduces the COD concentration of the wastewater from 10 to 14 g / L to 8.0 to 8.5 g / L, and the ammonia nitrogen concentration from 1900 to 2100 mg / L to 1850 to 1950 mg / L.

3. The advanced treatment process for thiourea-containing wastewater as described in claim 1, characterized in that, The anode of the three-dimensional electrochemical reactor is a DSA anode, the cathode is a titanium plate, and the reactor is filled with activated carbon three-dimensional particle electrodes. The power supply voltage is 20-30V, the reaction time is 0.3-0.7 hours, and aeration and mixing are carried out during the reaction process at an aeration rate of 4-6L / min, so that the COD concentration of the wastewater is reduced to 4.5-5.0g / L and the ammonia nitrogen concentration is reduced to 400-450mg / L.

4. The advanced treatment process for thiourea-containing wastewater as described in claim 1, characterized in that, The ozone concentration in the ozone oxidation tank is 40-60 mg / L, and the reaction time is 0.3-0.7 hours, which reduces the COD concentration of the wastewater to 2.0-2.4 g / L and the ammonia nitrogen concentration to 120-140 mg / L.

5. The advanced treatment process for thiourea-containing wastewater as described in claim 1, characterized in that, The alkaline agent is a sodium carbonate solution, and the dosage is 0.8-1.2 g / L of wastewater, which raises the pH value of the wastewater from 1-1.5 to 6-8.

6. The advanced treatment process for thiourea-containing wastewater as described in claim 1, characterized in that, The internal circulation ratio of the anaerobic internal circulation reactor is 150% to 250%, and the reaction time is 20 to 28 hours, which reduces the COD concentration of the wastewater to 1.4 to 1.6 g / L and the ammonia nitrogen concentration to 45 to 55 mg / L.

7. The advanced treatment process for thiourea-containing wastewater as described in claim 1, characterized in that, The biological contact oxidation tank is equipped with biological packing material, and the reaction time is 20 to 28 hours. During the reaction, aeration is carried out at a rate of 3.5 to 5.5 L / min, which reduces the COD concentration of the wastewater to 350 to 400 mg / L and the ammonia nitrogen concentration to 20 to 25 mg / L.

8. The advanced treatment process for thiourea-containing wastewater as described in claim 1, characterized in that, The ozone contact oxidation tower is filled with aeration packing material with a filling rate of 70% to 90%, the ozone dosage is 40 to 60 mg / L, the reaction time is 0.5 to 1.5 hours, the aeration rate is 3.5 to 5.5 L / min, and the final effluent COD concentration is reduced to 110 to 120 mg / L and the ammonia nitrogen concentration is reduced to 8 to 10 mg / L.

9. A deep treatment system for thiourea-containing wastewater, employing the deep treatment process as described in any one of claims 1-8, characterized in that, Including those connected sequentially: Iron-carbon micro-electrolysis tower is used for the preliminary oxidation and chain breaking of long-chain organic matter in wastewater; A three-dimensional electrochemical reactor is used to directly oxidize organic nitrogen in wastewater into nitrogen gas and further degrade organic matter; Ozone oxidation ponds are used for the deep oxidation of residual organic matter and incompletely oxidized organic nitrogen in wastewater. A pH buffer tank is connected to an alkali dosing device, which is used to add alkaline agents to the pH buffer tank to adjust the pH value of the wastewater. Anaerobic internal circulation reaction tower is used for denitrification and degradation of short-chain organic matter; Biological contact oxidation tanks are used to carry out nitrification to convert ammonia nitrogen into nitrate and degrade residual organic matter; Ozone contact oxidation towers are used for the final oxidation of residual recalcitrant organic matter in wastewater.

10. The advanced treatment system for thiourea-containing wastewater as described in claim 9, characterized in that, A nitrification liquid return pipeline is connected between the anaerobic internal circulation reactor and the biological contact oxidation tank. The return pipeline is used to transport the nitrification liquid produced by the biological contact oxidation tank to the anaerobic internal circulation reactor.

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